Problem: Constraints

* H is an integer between 2 and 50 (inclusive).
* W is an integer between 2 and 50 (inclusive).
* s_{i, j} is `.` or `#` (1 \leq i \leq H, 1 \leq j \leq W).
* s_{1, 1} and s_{H, W} are `.`.

Input

Input is given from Standard Input in the following format:


H W
s_{1, 1}s_{1, 2}s_{1, 3} ... s_{1, W}
s_{2, 1}s_{2, 2}s_{2, 3} ... s_{2, W}
:   :
s_{H, 1}s_{H, 2}s_{H, 3} ... s_{H, W}


Output

Print the maximum possible score that Snuke can achieve, or print -1 if the game cannot be completed.

Examples

Input

3 3
..#
#..
...


Output

2


Input

3 3
..#
..
...


Output

2


Input

10 37
.....................................
...#...####...####..###...###...###..
..#.#..#...#.##....#...#.#...#.#...#.
..#.#..#...#.#.....#...#.#...#.#...#.
.#...#.#..##.#.....#...#.#.###.#.###.
.#####.####..#.....#...#..##....##...
.#...#.#...#.#.....#...#.#...#.#...#.
.#...#.#...#.##....#...#.#...#.#...#.
.#...#.####...####..###...###...###..
.....................................


Output

209

Solution (in PYTHON3):

Solution:
H, W = map(int, input().split())
maze = ['#'*(W+2)]
for _ in range(H):
  maze.append('#'+input()+'#')
maze.append('#'*(W+2))

cost = [[-1]*(W+2) for _ in range(H+2)]
cost[1][1] = 0

que = [(1,1)]
while que:
  i,j = que.pop(0)
  if (i,j) == (H,W):
    break
  for k,l in ((i-1,j), (i+1,j), (i,j-1), (i,j+1)):
    #print(maze[k][l], cost[k][l])
    if maze[k][l] == '.' and cost[k][l] == -1:
      cost[k][l] = cost[i][j] + 1
      que.append((k,l))

if cost[H][W] == -1:
  print(-1)
else:
  n = -2 # .の数数
  for i in range(1,H+1):
    for j in range(1,W+1):
      if maze[i][j] == '.':
        n += 1
  print(n - cost[H][W] + 1)